How do I choose how tightly to fasten the belt so that it fixes the chest but does not interfere with breathing? — Men's bra / porous / type 155M-3

According to the product card, the adjustable hook-and-loop fasteners and straps allow you to fit the support as needed and ensure reliable fixation: the support is placed around the chest and the adjustable fasteners are fastened so that the pressure is suitable (according to the English description – comfortable and supportive); it can be worn over clothing. The manufacturer gives no specific guidance on the degree of tightening. According to the English description, if discomfort increases or breathing becomes difficult, the support must be removed immediately and a doctor consulted.

General recommendations (not a manufacturer's instruction): after putting it on, take a few calm breaths – the chest should expand freely; if breathing is difficult, loosen the fasteners; turn slightly and bend over – if the support noticeably shifts, tighten it a little more. The support is an orthopaedic device which, according to the English description, should be used on the advice of a doctor or physiotherapist; in case of a fresh injury, severe pain or a post-operative condition, agree the degree of fixation and the wearing regimen with your doctor.